Comparison of the observed [O/Fe] vs. [Fe/H] (left panel) and [Mg/Fe] vs. [Fe/H] (right panel) ratios of the thick disc stars, with the predictions of models with different IMF parameters as listed in Table 4. We see that increasing M_UP, so as to include the contributions of VMO (winds, PPISN and PISN), thick-disc stars can be reproduced pretty well. Moreover, changing both the IMF slope and M_UP, different populations can be recovered.